The magnifying power of a telescope is . When it is adjusted for parallel rays the distance between the objective and eyepiece is . The focal length of the lenses is:
1.
2.
3.
4.
1. | virtual, upright, height cm |
2. | real, inverted, height cm |
3. | real, inverted, height cm |
4. | virtual, upright, height cm |
1. | Difference between apparent and real depth of the pond |
2. | Mirage on hot summer days |
3. | Brilliance of the diamond |
4. | Working of optical fibre |
A ray of light travelling in a transparent medium of refractive index falls on a surface separating the medium from the air at an angle of incidence of . For which of the following value of , the ray can undergo total internal reflection?
1.
2.
3.
4.
A lens having focal length and aperture of diameter forms an image of intensity . An aperture of diameter in central region of lens is covered by a black paper. The focal length of lens and intensity of the image now will be respectively:
1. and
2. and
3. and
4. and
Two thin lenses of focal lengths f1 and f2 are in contact and coaxial. The power of the combination is:
1.
2.
3.
4. None of the above
A boy is trying to start a fire by focusing sunlight on a piece of paper using an equiconvex lens of a focal length of cm. The diameter of the sun is m and its mean distance from the earth is m. What is the diameter of the sun's image on the paper?
1. | m | 2. | m |
3. | m | 4. | m |
1. | 2. | ||
3. | 4. |
A microscope is focused on a mark on a piece of paper and then a slab of glass of thickness 3 cm and a refractive index 1.5 is placed over the mark. How should the microscope be moved to get the mark in focus again?
1. 1 cm upward
2. 4.5 cm downward
3. 1 cm downward
4. 2 cm upward
A convex lens and a concave lens, each having the same focal length of 25 cm, are put in contact to form a combination of lenses. The power in dioptres of the combination is:
1. 25
2. 50
3. infinite
4. zero